1. Field of the Invention
The present invention relates to night vision systems, and more particularly, to an insert for an eyecup of a night vision goggle which enables the eyecup to be removably secured to the goggle.
2. Description of Related Art
Night vision systems are commonly used by military and law enforcement personnel for conducting operations in low light or night conditions. These systems comprise goggles employing an image intensification process which amplifies the ambient light reflected or emitted by an observed object. The image intensification process involves conversion of the received ambient light into electron patterns and projection of the electron patterns onto a phosphor screen for conversion of the electron patterns into light visible to the observer. This visible light is then viewed by the operator through a lens provided in the eyepiece of the goggle.
It is necessary to prevent others from seeing the light emitted from the phosphor screen through the eyepiece, otherwise the night vision system would inadvertently give away the position of the operator. To accomplish this, the eyepiece is typically shrouded by an eyecup which surrounds the eyepiece. The typical eyecup adapts to the eyepiece of the night vision system, and has a bell-shaped portion which fits around the operator's eye. A flexible material, such as rubber, is commonly used to form the eyecup. The eyecup may also have a bellows portion which enables the shape of the eyecup to be easily deformed to adapt the goggle for each particular operator. A typical eyecup is disclosed in U.S. Pat. No. 4,698,857, issued to Kastendieck et al ("the '857 patent").
One drawback of the typical eyecup involves its attachment to the eyepiece. In the '857 patent, an internal annular groove and ridge are provided at the connecting end of the eyecup. The ridge is stretched over an external flange provided on the eyepiece, so that the flange seats in the groove. It is necessary to insure that the external flange completely engages the annular groove, otherwise the eyecup could become inadvertently dislodged from the goggle, greatly increasing the risk of someone seeing the light emitted from the eyepiece.
The elasticity of the rubber material is advantageous in that it readily conforms to the shape of the operator's face to form a light secure seal. However, a degree of design flexibility is lost by the choice of material to mate with the flange of the eyepiece. Since the annular groove and ridge are directly molded into the rubber eyecup material, the eyecup cannot be easily adapted to different size eyepieces. The diameter of the eyepieces can differ significantly to accommodate different power lenses. Thus, each size eyepiece requires a uniquely designed eyecup. Furthermore, rubber does not have good environmental, temperature and durability characteristics in comparison to other materials which could be used to form the connection between the eyepiece and the eyecup.
An additional problem with the prior art eyecup is that it can be cumbersome to remove and install the eyecup from the eyepiece of the night vision system. An operator may occasionally need to remove the eyecup from its attachment with the night vision system so as to clean the lens or the eyecup itself. Since this operation would typically occur at night, it could be difficult for the operator to manipulate the eyecup onto the attachment flange. The soft rubber material of the eyecup would not provide any tactile response to the operator confirming that the attachment has been properly made.
Thus, it would be desirable to provide an eyecup having an insert of an alternative material for attachment to the associated eyepiece of a night vision system. It would also be desirable to provide an eyecup which is easy to install and remove from an eyepiece of a night vision system, and which provides tactile feedback to the operator informing that the attachment is properly made. It would be further desirable to provide an insert for an eyecup which enables the eyecup to interface with varying size flanges typically provided on an eyepiece of a night vision system.